This invention is directed to a process and apparatus for reducing the volume and mass of solid waste, and more particularly, to converting a major portion of solid wastes into a liquefied waste which is separated and discharged through a conventional sewage system.
With the advent of throw-away products, the final disposal of such products has become a problem to which considerable attention need be given. For example, since their introduction in 1961, disposable diapers have become very popular, becoming a $3 billion dollar a year industry with an estimated 85 percent of America's mothers using them. Increasingly, the disposable diaper and other disposable products have become a prime target of environmentalists who say the throw-away products lead to rapid filling of solid waste dumps and contribute to problems such as ground water contamination. Legislation to either ban or restrict disposable diapers is before the legislatures of at least a dozen states. Disposable diapers account for only 2 percent of the nation's trash, but they will last approximately 500 years in a landfill. One proposed solution is a more expensive disposable diaper which is said to be biodegradable in a landfill since it is based on corn starch. However, these biodegradable diapers may not be sufficiently decomposable in landfills because there is not enough moisture or oxygen available. Another solution is the return to cloth diapers. However, there are not enough cloth diapers or cloth diaper services in the country to accommodate the demand.
Numerous waste disposal methods for solid refuse have been proposed. U.S. Pat. No. 3,736,120 discloses a multi-step process. One of the steps includes digesting organic material in a finely ground condition to convert it to a fertilizer having a high nitrogen content. Enzymes are added in a controlled process which utilizes actinic light generated from rare gas light tubes and anaerobic fermentation.
U.S. Pat. No. 4,110,281 discloses a process for producing a compost which comprises grinding municipal waste, magnetically freeing iron contained in the waste, separating the mixture into components of various sizes by fractionation, and treating the mixture in a fermentation process.
Fisk (U.S. Pat. No. 3,847,803) has proposed a process in which biodegradable material in a sewage sludge is subjected to aerobic fermentation in the presence of bacteria and enzymes.
Japanese Patent Publication 89-156,574 has proposed treating sludge by pulverizing solids and reacting the material with an organic-polymer decomposing enzyme before an anaerobic digestion step.
U.S. Pat. No. Re. 28,677 discloses a mechanical process for size reduction of solid waste. The solid waste material is ground to a point where there is size reduction that can be pumped in a fluid form.
The prior art has been directed mainly to the use of mechanical processes for preliminarily separating the solid waste into components for further waste disposal treatment. While the prior art has applied various processes and apparatuses for waste treatment, the prior art has not provided a process of or which is satisfactory for substantially reducing the volume and mass of solid wastes, particularly such wastes as disposable products having substrates of absorbent material, such as disposable diapers and under pads from hospitals and nursing homes. These throw-away products represent a significant burden on landfills as well as create odor and health problems during temporary storage and transport. The cost of landfill space is increasing and there is much public concern over health problems associated with landfills.
Accordingly, an object of the invention is to provide a process and apparatus for solid waste disposal wherein a preliminary enzymatic digestive process is used for separating solid waste into components that are more amenable to subsequent disposal or treatment than the components leaving a purely mechanical preliminary process.
Another object of the invention is to provide a process and apparatus for solid waste disposal wherein a preliminary enzymatic digestive process is used for separating solid waste into liquefied and residual solid waste forms to be handled more efficiently in subsequent disposal processes.
Another object of the present invention is to provide a process and apparatus for reducing the mass and volume of disposable solid waste so that a major portion may be converted into a liquefied form for subsequent conventional treatment.
Another object of the present invention is to provide a process and apparatus for reducing the mass and volumes of solid waste by using a preliminary enzymatic digestion process to convert a major portion of the solid waste into a liquefied form.
Another object of the invention is to provide a process and apparatus for reducing the mass and volume of disposable solid waste by first subjecting the solid waste to an enzymatic digestive process that converts a major portion of the solid waste into a liquefied waste which can be discharged through a conventional sewage system, and the residual solid waste is removed for further mechanical processing.